The following description of the prior art is not intended to be, nor should it be interpreted as, an indication of the common general knowledge pertaining to the invention, but rather to assist the person skilled in the art in understanding the developmental process which led to the invention.
Spray nozzles have been described having a nozzle body extending from a fluid inlet end to a fluid outlet end. The interior of the nozzle body forms a housing defining a central bore extending through one or more counterbores and/or chambers. The nozzle body may receive a nozzle cap to retain the inserted devices. The nozzle cap may house various inserted flow modification devices, such as a swirl chamber, an orifice disc and the like.
In prior art devices, the outlet (the face proximal to the outlet) of an orifice disc has been described as abutting a landing defined by a peripheral flange of a nozzle cap extending radially inwardly towards the central bore axis. A flat washer compression seal can be provided between orifice disc and the nozzle cap. Such washer seals, however, do not provide for particularly reliable sealing at elevated pressures and temperatures. Particularly deleteriously, the flat seal may be squeezed out from its mating surfaces and, worse, may enter the material flow.
An O-ring seal groove arrangement has been described in which the groove is situated in a lower peripheral flange of the nozzle cap. This arrangement may conform to sealing gland dimension standards and provide satisfactory sealing between the orifice disc and nozzle cap. However, this arrangement requires that the wall thickness between be the base of the groove and the outer nozzle cap surface be reduced, taking into account other design constraints such as the need to provide an outer nozzle profile that does not impede the spray pattern emitted from the orifice disc. Accordingly, this arrangement compromises the mechanical strength of the nozzle cap peripheral flange, a critical structural element in a spray nozzle arrangement. In such arrangements, the nozzle cap has an O-ring groove and the orifice disc abuts the peripheral flange of the nozzle cap inboard of the O-ring groove. The outer periphery of the orifice disc is free and unsupported at the outer O-ring groove. The orifice disc outer diameter is smaller than the accommodating internal diameter of the nozzle body chamber housing same to provide clearance and facilitate service and removal of the orifice disc—the internal components and elements of the nozzle body may be gummed up by hard-dried or set flow material and suitable clearance in prior art arrangements between the orifice disc and the nozzle cap chamber is generally required. Furthermore, this arrangement provides little mechanical support for the compressive forces required to create an adequate seal face to face without gaps. The arrangement is therefore less than ideal for high pressure operations.
Accordingly, arrangements have been described in which an O-ring groove has not been included in the nozzle cap for the proper sealing of the parts and sealing member is simply provided in a compression arrangement in the manner of a flat washer or gasket. Instead a gap is included as a design feature between the orifice disc and the nozzle cap in the fully assembled spray nozzle. Such an arrangement is not suitable for high pressure applications.
Accordingly, an object of the invention is to overcome one or more of the disadvantages encountered in previously described spray nozzle arrangements or to at least provide a useful alternative thereto.